1. Field of the Invention
The present invention relates to a seat reclining device for a vehicle, and more particularly, the present invention relates to a seat reclining device for a vehicle which is configured to allow an angle of a vehicle seat back to be continuously adjusted as desired in forward and rearward directions for ensuring comfort of an occupant.
2. Description of the Related Art
A vehicle seat functions to ensure comfort of an occupant. The vehicle seat is provided with a seat reclining device which allows an angle of a seat back to be adjusted in forward and rearward directions in conformity with a desire of an occupant, that is, a passenger or a driver.
The seat reclining device is arranged at a region where a seat cushion frame and a seat back frame which constitute a seat are connected with each other. By manipulating a lever of the seat, projecting sideward, the seat back can be adjusted in its angle with respect to the seat cushion.
A conventional seat reclining device will be disclosed below with reference to FIGS. 1 and 2.
The conventional seat reclining device 1 includes a plate holder 2 which is fastened to a rear end of a seat cushion frame and a toothed bracket 4 which is fastened by the medium of an upper bracket 3 to a lower end of a seat back frame. An operating section is interposed between the plate holder 2 and the toothed bracket 4. The toothed bracket 4 is formed with first teeth 10. A manipulating section is externally coupled to the plate holder 2. The manipulating section comprises a shaft 6, a manipulating lever 7, a lever spring 8 and a return spring 9.
The operating section comprises a pair of operating members 12, a cam lever 13 and a cam plate 14. The operating members 12 are placed in a space defined between the plate holder 2 and the toothed bracket 4. The operating members 12 are formed with second teeth 11 in a manner such that the second teeth 11 can be meshed with and separated from the first teeth 10 formed in the toothed bracket 4 so as to permit and prevent reclining of a seat back. The cam lever 13 functions to move the operating members 12 in a manner such that the second teeth 11 are meshed with the first teeth 10, and the cam plate 14 functions to move the operating members 12 in a manner such that the second teeth 11 are separated from the first teeth 10.
The cam lever 13 is formed with a pair of cams 15. The cams 15 function to push the operating members 12 in a direction where the second teeth 11 are meshed with the first teeth 10. The operating members 12 are defined with a pair of cam grooves 16 for respectively receiving the cams 15 when it is necessary to separate the second teeth 11 from the first teeth 10.
Two pairs of projecting pins 17 are formed on the operating members 12 and the cam lever 13. A pair of slots 18 are defined in the cam plate 14 in a manner such that one pair of projecting pins 17 which are respectively formed on the operating members 12 are inserted into the pair of slots 18. Also, a pair of pin holes are defined in the cam plate 14 inward of the slots 18 in a manner such that the other one pair of projecting pins 17 which are formed on the cam lever 13 are inserted into the pair of pin holes.
Describing operations of the conventional seat reclining device 1 constructed as mentioned above, initially, the lever spring 8 and return spring 9 bias, via the cam lever 13, the operating members 12 in a manner such that the second teeth 11 of the operating members 12 are meshed with the first teeth of the toothed bracket 4.
In this state, when it is necessary to recline the seat back, by pulling upward the manipulating lever 7, the shaft 6 is rotated. Then, as the cam lever 13 coupled to the shaft 6 is rotated, the pair of cams 15 are respectively received in the cam grooves 16 defined in the operating members 12. Also, as the cam plate 14 coupled to the shaft 6 is rotated with the projecting pins 17 of the operating members 12 inserted into the slots 18 of the cam plate 14, the second teeth 11 of the operating members 12 are separated from the first teeth 10 of the toothed bracket 4, whereby it is possible to recline the seat back.
However, the conventional seat reclining device 1 suffers from defects in that the number of component parts is increased, and thereby, assemblability and productivity of the seat reclining device 1 are deteriorated. Also, malfunction of the seat reclining device 1 can occur due to misassembly of the cam plate 14 which comprises a thin plate.
Specifically, in the conventional seat reclining device 1, since a chance that the seat back is abruptly and too forcefully reclined by the presence of the return spring. 9 is increased, even while being seated, an old or feeble person may feel a substantial amount of shock when the seat back is reclined forward.
Further, even if the manipulating lever 7 is pulled while a person is not seated, as the seat back is violently rotated forward, a manipulator such as a driver may be injured and an impulsive operating sound is generated.
Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a seat reclining device for a vehicle which is configured to be decreased in the number of component parts and to allow a vehicle seat back to be reclined only by an angle desired by a manipulator.
Another object of the present invention is to provide a seat reclining device for a vehicle which reduces a manufacturing cost, improves productivity, prevents a seat back from being abruptly and too forcefully reclined and operation noise from being generated, thereby protecting the human body from being injured, elevating quality of the seat reclining device and ensuring comfort of an occupant.
In order to achieve the above objects, according to one aspect of the present invention, there is provided a seat reclining device for a vehicle, arranged at a region where a seat cushion frame and a seat back frame, which constitute a vehicle seat having a seat cushion and a seat back, are connected with each other, to allow an angle of the seat back to be adjusted in forward and rearward directions, the device comprising: an upper toothed bracket fastened to a lower end of the seat back frame; a lower toothed bracket fastened to a rear end of the seat cushion frame; an operating section interposed between the upper and lower toothed brackets, for allowing the seat back to be reclined; and a cover plate for covering the upper and lower toothed brackets and the operating section; wherein the operating section comprises upper teeth internally formed on a circumferential inner surface of a groove which is depressed on the upper toothed bracket; lower teeth externally formed on a circumferential outer surface of a protrusion which projects from the lower toothed bracket toward the upper toothed bracket and is received in the groove of the upper toothed bracket, in a manner such that the lower teeth can be meshed with the upper teeth; a pair of cams accommodated in a cam hole which is defined at a center portion of the lower toothed bracket, to rotate the lower teeth of the lower toothed bracket in a desired reclining direction; and a cam spring having both ends which are respectively fitted into spring holes defined in the cams, to bias the cams in opposing radial outward directions; and wherein each cam has a shaft hole through which an operating shaft is fitted; a boss which is formed around the shaft hole on a surface of the cam; an operating cam part which is formed on a circumferential outer surface of the cam to extend through a first predetermined angle and is brought into contact with a circumferential inner surface of the lower toothed bracket, defining the cam hole, the operating cam part having an eccentric center which is deviated from a center of the cam hole, to serve as a kind of wedge; a concentric part which is formed on a surface of the operating cam part, farthest from the boss, to extend through a second predetermined angle less than the first predetermined angle, and has a stepped portion in a manner such that concentric parts of the pair of cams can be brought into contact with each other; and a key groove which is defined to be communicated with the shaft hole in a manner such that a key integrally formed on the operating shaft can be received in the key groove to operate the cam toward a recline permitting position.
According to another aspect of the present invention, the lower teeth has the number of teeth which is less than that of the upper teeth, in a manner such that a position of the upper toothed bracket can be changed by rotation of the lower toothed bracket.